plist is currently used by the scheduler, which only needs to know the
highest item in the list. This adds plist_last which allows you to
find the lowest. This is necessary for using plists to implement a
fast search of dynamic ranges in pm_qos which can have both highest
and lowest criteria.
Signed-off-by: James Bottomley <James.Bottomley@xxxxxxx>
---
include/linux/plist.h | 29 +++++++++++++++++++++++++++++
1 files changed, 29 insertions(+), 0 deletions(-)
diff --git a/include/linux/plist.h b/include/linux/plist.h
index 6898985..7254eda 100644
--- a/include/linux/plist.h
+++ b/include/linux/plist.h
@@ -260,6 +260,23 @@ static inline int plist_node_empty(const struct plist_node *node)
#endif
/**
+ * plist_last_entry - get the struct for the last entry
+ * @head: the &struct plist_head pointer
+ * @type: the type of the struct this is embedded in
+ * @member: the name of the list_struct within the struct
+ */
+#ifdef CONFIG_DEBUG_PI_LIST
+# define plist_last_entry(head, type, member) \
+({ \
+ WARN_ON(plist_head_empty(head)); \
+ container_of(plist_last(head), type, member); \
+})
+#else
+# define plist_last_entry(head, type, member) \
+ container_of(plist_last(head), type, member)
+#endif
+
+/**
* plist_first - return the first node (and thus, highest priority)
* @head: the &struct plist_head pointer
*
@@ -271,4 +288,16 @@ static inline struct plist_node *plist_first(const struct plist_head *head)
struct plist_node, plist.node_list);
}
+/**
+ * plist_last - return the last node (and thus, lowest priority)
+ * @head: the &struct plist_head pointer
+ *
+ * Assumes the plist is _not_ empty.
+ */
+static inline struct plist_node *plist_last(const struct plist_head *head)
+{
+ return list_entry(head->node_list.prev,
+ struct plist_node, plist.node_list);
+}
+
#endif
--
1.6.4.2
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